International chemical experts have gained samples from the site of a suspected chemical attack in Syria after waiting for more than a week in Damascus.

The team of inspectors from the Organisation for the Prohibition of Chemical Weapons left Damascus and headed to the nearby town of Douma on Saturday, the Russian Foreign Ministry said.

The inspection, now a fortnight after the alleged 7 April attack in which some 70 people were said to be killed, took place after repeated delays.

In a statement, the OPCW said it would now evaluate and consider whether the team needs to make a second visit to Douma. Samples will be transported back to the Netherlands and onward to the organisation's network of designated labs for analysis.

Based on the analysis of the sample results as well other information and materials collected by the team, the mission would compile a report and submit it to the organisation's member states, the statement said.

The chemical inspectors from several countries have been in Damascus for a week waiting for clearance to visit the town.

Several Western states claim that Syria and its Russian allies had blocked the inspectors from entering Douma.

Earlier in the week, their visit to Douma was delayed after their UN security team came under fire at the location.

A UN official told the AFP news agency that "shots were fired yesterday at a UN security team doing a reconnaissance in Douma ... They were not injured and returned to Damascus."

Chemical experts told Middle East Eye that repeated delays could lead to the evidence from the suspected chemical attack blowing "away in the wind".

"You can’t prove chlorine at this point, even if you dig up dead bodies," Dan Kaszeta, a chemical weapons expert at Strongpoint Security, told MEE on Friday.

Chlorine – which Bellingcat has concluded, through open source information, was "most likely" used in one of the air strikes – is hard to find after an attack because it is a gas, Kaszeta said.

"It blows away in the wind," he said. "If you take a bunch of swimming pool water and throw it on the ground and wait three days, it would look exactly the same."

Both Russia and Syria reject claims that chemical weapons were used. Moscow has offered several narratives on Douma, claiming simultaneously that there never was an attack and that it was the work of rebels in the area.

France has said it is "very likely" that proof has disappeared, and the US has accused the Russians and Syrians of tampering with evidence.

The OPCW has been investigating the use of toxic chemicals in Syria's civil war since 2014.